The present invention relates generally to interface devices between humans and computers, and more particularly to computer interface devices that provide force feedback to the user.
Computer systems are used extensively in many different industries to implement computer controlled simulations, games, and other application programs. More particularly, these types of games and simulations are very popular with the mass market of home consumers. A computer system typically displays a visual environment to a user on a display screen or other visual output device. Users can interact with the displayed environment to play a game, experience a simulation or xe2x80x9cvirtual realityxe2x80x9d environment, or otherwise influence events or images depicted on the screen. Such user interaction can be implemented through the use of a human-computer interface device, such as a joystick, xe2x80x9cjoypadxe2x80x9d button controller, mouse, trackball, stylus and tablet, foot or hand pedals, or the like, that is connected to the computer system controlling the displayed environment. The computer updates the game or simulation in response to the user""s manipulation of a moved object such as a joystick handle or mouse, and provides feedback to the user utilizing the display screen and, typically, audio speakers.
In some interface devices, haptic (e.g., tactile) feedback is also provided to the user, more generally known as xe2x80x9cforce feedback.xe2x80x9d These types of interface devices can provide physical sensations to the user manipulating the physical object of the interface device. Typically, motors or other actuators are coupled to the interface object and are connected to the controlling computer system. The computer system receives sensor signals from the interface device and sends appropriate force feedback control signals to the actuators of the interface device in conjunction with simulation/game events. The actuators then provide forces on the interface object. The computer system can thus convey physical sensations to the user in conjunction with other visual and auditory feedback as the user is grasping or contacting the object of the interface device. Force feedback interface devices can provide a whole new modality for human-computer interaction.
Force feedback input/output (I/O) devices of the prior art have concentrated on providing maximum haptic fidelity, i.e., the realism of the haptic feedback was desired to be optimized. This is because most of the force feedback devices have been targeted at the specific needs of highly industrial or scientific applications, and not a mass consumer market. To attain such realism, design concerns useful the mass market such as low size and weight, low complexity, programming compatibility, low cost, and safety have been sacrificed in the prior art. As a result, typical force feedback interface devices include complex robotic mechanisms which require precise, bulky, and expensive components that have significant power requirements and are difficult to program for applications.
In addition, the prior art force feedback devices typically use a host computer to close a control loop around the system to generate sensations and maintain safety and stability through direct host control. FIG. 1 illustrates a block diagram of a control system 2 having a typical host controlled loop. A user manipulated object 3, such as a joystick or similar object, is moved by a user to interface with a host computer 4 with a display device 5. Sensors 6 detect the position of the user object in provided degrees of freedom and may also include buttons or other controls that detect user actions such as the press of a button. The sensor data including positional and button data is sent to host computer 4 over a bi-directional communication bus 7 that is typically connected to an interface card plugged into the host computer. To complete the control loop, host computer 4 sends force commands over bus 7 to actuators 8, and the actuators output forces on the object 3 to the user. The functions of reading sensor data and outputting force values to actuators 7 can be a burden on the host processor which detracts from the performance of the host in other host tasks and application execution.
An important concern for a force feedback interface device is communication bandwidth between the controlling computer and the interface device. To provide realistic force feedback, the complex devices of the prior art typically use high speed communication electronics that allow the controlling computer to quickly send and update force feedback signals to the interface device. The more quickly the controlling computer can send and receive signals to and from the interface device, the more accurately and realistically the desired forces can be applied on the interface object. In addition, using a high bandwidth communication interface, force feedback can be accurately coordinated with other supplied feedback, such as images on the video screen, and with user inputs such as movement of the object, activated buttons, etc.
A problem is evident when prior art force feedback interface devices are provided to the mass consumer market. Most home computers have a built-in standard serial communication interfaces, such as an RS-232 interface, RS-422 interface, xe2x80x9cgame portxe2x80x9d, Universal Serial Bus interface, or Ethernet interface that may conveniently be used to connect peripherals like a force feedback interface device to the host computer. In addition, manufacturers prefer to provide peripheral devices that use these serial interfaces, since no additional hardware, such as interface cards, needs to be provided with such peripherals. The manufacturing cost of the peripheral device can thus be significantly reduced. However, these standard serial communication interfaces are typically quite slow (i.e. have low bandwidth) compared to other communication interfaces. Realistic and accurate force feedback thus becomes difficult to provide by a controlling computer system to a prior art interface device connected through such a serial interface in comparison with other interfaces such as a direct interface card (e.g., ISA or PCI card) connecting to the data bus of the host computer.
Another important concern in the mass market industry is the issue of user safety. Because a force feedback device can impart physical forces upon the user, the potential for injury must be carefully addressed. To provide a safety measure for the user, the force feedback devices of the prior art typically include a safety or xe2x80x9cdeadmanxe2x80x9d switch which the user must activate to allow forces to be applied to the user manipulable object. If the user does not close the switch, no forces can be output. The safety switches of the prior art are typically a button or a pedal which the user must continually press or hold down to allow power to be received by the actuators. However, such safety switches can be cumbersome and/or tiring for the user to close, since the user must constantly maintain a particular grip or position to feel forces. In addition, these types of safety switches are easy to defeat by users; for example, an elastic band can be wrapped around a safety button to keep the button depressed, which defeats the entire safety purpose of the safety switch.
Finally, mass market force feedback interface devices must necessarily be low cost devices that are simple to manufacture so that the device is competitively priced in the high volume, aggressive home computer and home video game markets.
The present invention is directed to implementations of a human/computer interface device for controlling and providing force feedback to a user. Several implementations are provided to decrease the cost in manufacturing an interface device and making the device safe for the high volume consumer market of computer and video game users.
More particularly, one embodiment of an interface apparatus and method of the present invention for interfacing motion of a user manipulable object with a host computer includes a user object, such as a joystick, physically contacted by a user and having at least one degree of freedom of movement. A device microprocessor local to the interface apparatus and separate from the host computer is coupled to the host by a first interface buses. The microprocessor receives host commands from the host computer on the first interface bus. An actuator applies a force along said degree of freedom to the user object in response to microprocessor force commands produced by the device microprocessor. A sensor for detecting a position of the user object along the degree of freedom and outputs sensor signals. The sensor signals are received by the host computer on a second interface bus separate from the first interface bus. The host computer updates a host application process, such as a simulation or video game, in response to the sensor signals.
Preferably, the first interface bus is an RS-232 interface bus or similar serial standard. The second interface bus is preferably a standard game port interface bus coupled to a game port of the host computer or the equivalent. Force feedback commands are sent by the host over the serial interface bus and the sensor signals are received by the host in the traditional way via the game port. The interface device can thus be used as a standard joystick without force feedback by utilizing only the game port interface in communication with the host computer, and allows backward compatibility for non-force-feedback functionality via standard game port drivers.
In some embodiments, the device microprocessor receives the sensor signals to compute force values to output to the actuators. A second sensor can be used to detect the position of the joystick independently of the host sensor and output sensor signals to the microprocessor. The local microprocessor receives high-level host commands and can implement independent force routines that receive sensor signals and compute forces. The force routines can be stored in memory local to the interface apparatus. Preferably, a button device is coupled to the interface apparatus that provides a button input signal to the microprocessor when the user presses the button. The microprocessor provides the button input signal to the host computer over the game port interface bus. In addition, the microprocessor preferably deactivates the actuator when at least one of the multiple interface buses is disconnected from the host computer or disconnected from the interface apparatus.
In a different xe2x80x9crecoilxe2x80x9d embodiment of the interface apparatus, the interface device includes an actuator that applies a force on the user object. A user-selectable control, such as a button provided on the joystick, sends an activation signal to the actuator when the user activates the button and thereby instructs the actuator to apply the force on said user object in a reflex process independent of the host computer. This force, for example, can be a recoil or jolt that is output whenever the user selects the button. In one embodiment, the actuator applies the force on the joystick only when the user activates the button. In a different embodiment, the host computer is coupled to the actuator by a second interface and transmits an enable signal to the joystick. the actuator applies the force only when the user activates the button and when the enable signal is provided. In a yet another embodiment, the host computer may additionally send a simple activation signal to the actuator to command the actuator to apply the force to the user object regardless of whether the button is pressed by the user. The host can control the actuator using only a very small amount of information, and can use a parallel interface or a serial port used as a parallel interface. A user enable switch on said interface device can, when selected or deselected by the user, enable or disable the recoil reflex process.
In a different, more complex xe2x80x9crecoilxe2x80x9d embodiment, the host computer can send a greater amount of control signals and/or other information to the actuators than in other recoil embodiments of the interface device by providing the control signals serially. One or more shift registers covert the serial data to parallel information that is provided to programmable logic. The logic sends the control signals, such as enable and activation signals, to the actuator and other components as necessary. A sensor outputs sensor signals to the host computer via a second interface bus as described above.
A force feedback interface device of the present invention for safe use by a user includes a sensor for sensing a joystick""s position and an actuator for applying a force to the joystick. A safety switch is coupled to the joystick for disabling the actuator when the user is not using the interface device. One safety switch of the present invention enables the actuator when an amount of weight over a predetermined amount is placed on the joystick, such as the amount of weight created by a user grasping the joystick. The joystick includes a handle portion translatably coupled to a base portion. The safety switch includes a contact on the handle portion and a contact on the base portion such that when the predetermined amount of weight is applied to the joystick, the contacts engage to allow electrical current to flow. A spring member forces the portions apart from each other when less than the predetermined amount of weight is applied to the joystick. A different touch plate safety switch feature similarly allows the actuators to be powered only when the user is touching the provided touch plates. A separate break-away joystick safety feature can also be included which comprises a safety break handle that breaks off from the interface apparatus when a force over a predetermined threshold is applied to the joystick. The safety break-away handle can be attached to the interface apparatus, for example, by magnets.
A circuit of the present invention for storing power in a force feedback interface device that interfaces a user with a host computer system includes a capacitor for storing power provided by a signal input to the circuit. A sensing device coupled to the capacitor senses when the capacitor is fully charged by monitoring the input signal to determine when the capacitor is fully charged. A control device provides a control signal to a driver and actuator so that the actuator can apply force to a user object of the interface device. The stored power from the capacitor is supplied to the actuator when applying the force. A current limiter limits the current of the input signal and provides the limited current to the capacitor. The input voltage signal can be received from a game port interface bus coupled to the host computer system or from a power supply included in the interface device.
The interface apparatus of the present invention includes several low cost components that are suitable for providing accurate force feedback for the high volume home consumer market and similar markets. The use of the parallel combination of a serial bus and a game port bus, coupled to two ports of the host computer system, allows one bus to be used to send signals to the host and the other bus to receive force commands from the host, thus providing a very low cost system having realistic force feedback. The local device microprocessor processes commands independently of the host computer, thus saving significant processing time on the host computer. Other low cost embodiments require no or minimal force commands from the host, allowing simple force feedback to be provided to users. The power circuit of the present invention allows smaller power supplies to be used or eliminates the need for a power supply.
The safety features of the present invention herein also are important when supplying force feedback devices to the home consumer market. The hand-weighted safety switch allows a user to conveniently operate the interface device and provides necessary safety shut-down features. The communication line safety feature allows the actuators to be deactivated in the event of a disconnection between interface device and host computer. These improvements allow a computer system to provide accurate and realistic force feedback in a safe, low-cost low bandwidth communication interface and is thus ideal for the mass market of computer and game systems.
These and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following specification of the invention and a study of the several figures of the drawing.